<html>
    <head>
        <script type="text/javascript">
            function Mostrar()
            {
                var objeto=document.getElementById("mySelect");
                var option=document.createElement("option");
                var MiVariable=prompt("Ingresa Direccion")
                option.text=MiVariable;
                try
                {
                    // for IE earlier than version 8
                    objeto.add(option,objeto.options[null]);
                }
                catch (e)
                {
                    objeto.add(option,null);
                }
            }
        </script>
    </head>
    <body>

        <form id="form9" name="form9">
            <select id="mySelect" size="5" onchange="document.getElementById('form9').submit();">
            </select>
        </form>

        <button type="button" onclick="Mostrar()">Insertar direccion</button>

    </body>
</html>
